234 B eaamontite and Lincolnite identical with Heulandite. 



tises on mineralogy, nor am I aware that any notice has been ta- 

 ken of it in the American Journal of Science. 



On comparing the crystals of this substance, with several of 

 those of the Heulandite of Nova Scotia, which presented a modi- 

 fication rather uncommon, I was satisfied that they were both 

 derived from the similar replacement of the acute lateral edges, 

 and obtuse solid angles, of the same primary right oblique angled 

 prism ; the planes /, which in most instances are small, being 

 now so extended as to reduce the length of the figure to nearly 

 the same dimensions with its breadth ; thus giving rise to what 

 might, at first sight, appear to be a square prism, terminated by 

 two obtuse four sided pyramids, resting upon the opposite lateral 

 faces of the crystal, as I have endeavored to represent by the sub- 

 joined figure 2. The planes a a' : being carried to the extreme, 



so as to entirely obliterate the edge formed by the planes M and T, 

 of the right oblique prism, fig. 1, — the pyramids thus resulting, 

 are very beautiful in both minerals, particularly in the Beaumont- 

 ite, and they present the same characteristic vitreous lustre, con- 

 trasted with the soft, pearly white reflection of the planes P, 

 which we always observe in the crystals of this mineral from 

 other localities. Both minerals, however, present shades of brown 

 and yellow. On further comparing their hardness and pyrognos- 

 tic characters, and failing also to obtain any other cleavage in the 

 Baltimore specimens, than that well known in Heulandite. I could 

 have but little doubt that M. Levy, (unless he had described 

 some other very analogous mineral from this locality, which I 

 have not seen,) had been misled by its unusual crystalline form, 

 and, instead of making known a new species, had only given us 

 the wrong characters of an old one. I am sure that he would 

 not have been led into a mistake of this kind, had the crystals 

 examined by him presented those gradual changes which have 

 ultimately given rise to the figure supposed by him to be the 

 primary right square prism of the Beaumontite, and which we so 

 readily observe in the crystals from Nova Scotia. 



